Marek Chrobak, Ming Li. k+1 Heads Are Better than k for PDAs. J. Comput. Syst. Sci., 37(2):144-155, 1988.
@article{ChrobakL88, title = {k+1 Heads Are Better than k for PDAs}, author = {Marek Chrobak and Ming Li}, year = {1988}, researchr = {https://researchr.org/publication/ChrobakL88}, cites = {0}, citedby = {0}, journal = {J. Comput. Syst. Sci.}, volume = {37}, number = {2}, pages = {144-155}, }